1. The Field of the Invention
This invention relates to a method for casting concrete, plaster and materials. More particularly, this invention relates to a method of producing cast materials using a primary mold comprising a flexible membrane, which in its relaxed state comprises the shape of a bag or balloon, and optionally, a second fixed mold. The present invention also relates to the products formed by this process.
2. Description of the Related Art
Numerous methods have been proposed over the years for casting concrete, plaster and other castible materials in molds. Some methods have also proposed the use of a sheet of flexible material in conjunction with a fixed mold to produce panels of cast material.
For example, U.S. Pat. No. 3,910,547 to Varriano discloses a method of casting panels wherein a panel mold form is provided and a thin flexible film is disposed over the top of the mold and is pulled taut parallel to the bottom of the mold. When casting material is added to the mold, it is placed on top of the thin film which, due to the weight of the casting material, deforms down to fill the mold. Feature strips or other design items can be provided in the bottom of the mold to impart design features into the cast panel. The method of the Varriano patent is to produce panels wherein the dimensions of the panel in directions parallel to the plane of the membrane prior to addition of the casting material is greater than the dimension of the panel perpendicular to the plane of the membrane prior to the addition of the casting material.
U.S. Pat. No. 3,492,384 to Matthews et al. discloses a method of casting materials in which a sheet of a resilient and flexible membrane is arranged over a mold form. The membrane is drawn into contact with the mold form by applying negative pressure to the mold side of the membrane and the membrane is allowed to take the shape of and follow the contours of the mold form. The moldable material is placed on the membrane in the mold form and allowed to set, during which time the negative pressure on the membrane is maintained. The Matthews patent as with the Varriano patent only discloses a method for application to making panel type materials wherein the dimensions of the material parallel to the plane of the membrane is greater than the depth or height of the material perpendicular to the membrane.
In U.S. Pat. No. 985,353 to Landis another similar method is disclosed. In the Landis patent, a method is disclosed for casting panels having surfaces resembling the outlines of natural, broken, rough-hewn stone. A panel mold is provided in the bottom of which is provided an array of irregular materials so as to impart an irregular surface to the material cast in the mold. The irregular materials at the bottom of the mold are covered by a flexible sheet. Casting material is added to the mold on top of the flexible material.
The prior art processes fail to provide the numerous advantages of the present invention as discussed below.